1. Field of the Invention
The present invention relates to a vehicular use power feed apparatus for supplying power to various electrical components, devices, and apparatuses mounted in a vehicle, more particularly relates to a vehicular use power feed apparatus in which the route of the power fed to a plurality of electrical components is configured as a loop, trouble can be effectively detected, and the trouble portion cut out of the loop so that power can be fed to the other electrical components without hindrance.
2. Description of the Related Art
Recently, rapid progress has been made in the use of electronics in vehicles.
Vehicles, for example, various types of passenger cars, have been making increasing use of electronic control using microcomputers and other electronic circuits and electronic devices for the purpose of improvement of the fuel consumption of the internal combustion engine, automatic transmission, and other main equipment indispensable for operation (hereinafter referred to as the "main equipment"), reduction of the exhaust, smooth driving, and safe driving.
Further, experiments have been made with replacing the meters of the front panel with electronic display devices, for example, color liquid crystal display devices, to further facilitate recognition of the operating state of the vehicle and, at the same time, provide various information on the vehicle in various forms.
Further, there has been strong demand for greater improvement of the riding comfort and improvement of convenience of the vehicle as a means of transportation and, at the same time, use of the vehicle not only as a means of transportation, but also as a living space. Accordingly, in addition to the main equipment, there have been an increase in mounting of air-conditioners, position-locating and driving information devices using GPSS, automatic seat adjustment devices, power windows, wipers, door locks, various lamps, radios, CD players, TVs, entertainment equipment, and other auxiliary apparatuses and equipment (hereinafter referred to as "auxiliary equipment") and an increase in the electronic control of the same.
As described above, along with the electronic control of electrical components, main equipment, and auxiliary equipment mounted in vehicles, not only has there been an increase in the electrical components and the parts of the main equipment and auxiliary equipment per se which are electrically driven, but also various electronic devices have been mounted in the vehicles for the electronic control of the main equipment and auxiliary equipment.
Accordingly, the supply of power in the vehicle and the transmission of signals for operating the electronic control devices for these apparatuses and equipment mounted in the vehicle have become important.
In the supply of power and transmission of signals in a vehicle, however, when the power feed lines and signal lines (wire harness) are affixed by screws to the chassis or the like, the covering of the wire harness is sometimes broken resulting in contact of the inside conductor with the chassis and consequent short-circuiting. Alternatively, the wire harness may pass through the door or another swinging portion or pass through a moving portion etc. and thereby undergo fatigue and consequent disconnection or short-circuiting.
Breakage or short-circuiting of a power feed line or a signal line would cause a problem in that the main equipment or auxiliary equipment would no longer be able to normally operate. Therefore, various countermeasures have been proposed.
Japanese Unexamined Patent Publication (Kokai) No. 60-193764 discloses a technique calling for provision of a current sensor and a circuit breaker in the wire harness between a power source and load of a vehicle, detecting the unit current flowing from the power source to an electrical component or other load while the vehicle is stopped so as to detect abnormal states, and driving the circuit breaker when an abnormality is determined so as to cut off the load from the power source. Japanese Unexamined Patent Publication (Kokai) No. 60-193746 also describes that short-circuits of extents not melting the fuse can be detected. However, this method only covers abnormal states while the vehicle is stopped, so has the defect that it cannot be applied while the vehicle is being driven. Further, this method cannot pinpoint the position where the short-circuit occurs, therefore it is not possible to isolate the short-circuited portion and automatically restore the supply of power.
In one example of a vehicular use power feed apparatus of the related art, it has been proposed to connect a power feed line protected by a fuse, fusible link, or other power feed line protecting element to an electrical component for each subsystem so as to restrict the effect of a short-circuit etc. occurring in the power feed line to just that subsystem and thereby prevent other subsystems from being affected. With this technique, however, there is the problem that many power feed lines must be laid. In particular, as a practical problem, it is not easy to lay out many power feed lines in the restricted space of a vehicle.
Japanese Unexamined Patent Publication (Kokai) No. 57-80239 discloses a technique in which the power feed line is configured as a loop, a current sensor is provided at least at one position of the power feed line, an abnormal state detected by the current sensor is informed to a central control unit, the central control unit successively turns a plurality of power source control units on and off to identify (pinpoint) the position where the abnormality occurred, and the pinpointed position where the abnormality occurred is cut out of the power supply loop.
Japanese Unexamined Patent Publication (Kokai) No. 5-64361 discloses a technique in which two systems of power feed lines are laid and power is supplied via diodes so that power may be supplied from the problem-free power feed line even if the other power feed line is broken or short-circuits.
Japanese Unexamined Patent Publication (Kokai) No. 8-275408 discloses a backup system for power feed lines in which two systems of power feed lines are laid in parallel between the power source and a load and two relays for switching these two systems of power feed lines are provided. When a problem such as a short-circuit occurs in one power feed line system, the relay connects the other power feed line system and load.
In the centralized wiring apparatus for an automobile disclosed in Japanese Unexamined Patent Publication (Kokai) No. 57-80239, while the complexity of the configuration of the power feed lines is avoided, there is a problem that a long time is taken for detection of trouble and too long a time is taken for isolating the portion where the trouble occurred.
Namely, in this centralized wiring apparatus for an automobile, when an abnormality occurs, the entire system is reset once (state where no power is supplied), then restarted, therefore a state where no power is fed continues for a long time and real time backup is not possible. Further, in each power control unit, the power feed line is opened or closed at one contact, therefore there is the problem that when a portion whose function it is desired to maintain at all costs short-circuits, backup is not possible.
In the method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-64361, since two systems of power feed lines are laid, the wire harness becomes thick. It is difficult to lay such a wire harness in a restricted space. Further, large current diodes become necessary.
In the method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 8-275408, since two systems of power feed lines are laid for every group of loads switched by one relay, the wire harness becomes thick. Laying of such a thick wire harness in the restricted space of a vehicle is difficult. Particularly, since the two systems of power feed lines are provided for improvement of the reliability, desirably two such power feed lines should be separated from each other in position, but various practical problems are encountered when such a design concept is applied to the inside of a vehicle where space is so restricted.
Further, this method is almost useless against trouble such as disconnection of lines.
While the above explanation was given with respect to mainly power feed lines, similar problems to the above are encountered with signal transmission lines for transmission of control signals and the like.
As described above, there is strong demand for the effective supply of power to the electrical components, main equipment, auxiliary equipment, electronic control unit, and other loads and electronic apparatuses with a high reliability and for the establishment and maintenance of reliable signal paths in vehicles--where there are many limitations in space and practical problems in mounting.